Benzol scrubbing method and apparatus



Nov. 20, 1956 C. OTTO BENZOL SCRUBBING METHOD AND APPARATUS Filed April 12, 1954 2 Sheets-Sheet 2 INVENTOR. 6.4RL Orro United States Patent BENZOL SCRUBBING METHOD AND APPARATUS v Carl Otto, Manhasset, N. Y.

Application April 12, 1954, Serial No. 422,478

12 Claims. (Cl. 26122) The present invention comprises an improved method of and improved apparatus for successively bringing fluid, such as gas or air, flowing upward through a vertically elongated contact chamber or tower into contact with a liquid, as oil or water, sprayed into the upper end of said chamber and collected and resprayed into the tower at successively lower levels. The invention may be used with advantage for various purposes, such for example as in separating vapors, such as the light oil vapors collectively known as benzol, from coke oven gas, by scrubbing the latter with a vapor absorbing liquid; in cooling gas passing away from the hydraulic main of a by-product coke oven battery; in the distillation of ammonia liquor recovered in cooling, and eliminating tar from coke oven gas passing away from the hydraulic main of a by-product coke oven battery; and in scrubbing dust out of air or other gaseous substance.

In my prior application, filed June 22, 1948, which has matured into my Patent 2,675,215, granted April 13, 1954, I have disclosed a novel method of and apparatus especially designed for use in separating benzol from coke oven gas in the manner mentioned above. The method and apparatus disclosed and claimed in my said prior application is now in extensive and highly successful commercial use in this country.

The primary object of the present invention is to pro vide a scrubbing apparatus and method of the general type disclosed in my above mentioned prior application in which the pumping energy required to respray the scrubbing liquid into the scrubbing tower at the different levels may be substantially reduced without necessarily requiring changes in the location of the difierent spray nozzles, or in the volumes or velocities of the spray liquid discharged at the different levels. .The reduction in the total pumping energy made possible by the use of the present invention, is obtained as a result of a rearrangement of pipes associated with the pumps passing liquid to and through the difierent spray nozzles. The purpose and efiect of the piping rearrangement is to reduce the aggregate head of the spray liquid pumping load. The rearrangement will ordinarily result in a relatively unimportant increase in the aggregate piping length, and increases the number of pumps used in some forms of the invention but its not required with other forms of the invention.

The various features of novelty which characterize my invention are pointed out with particularity in the claims annexed to and forming a part of this specification. For a better understanding of the invention, however, its advantages, and specific objects attained with its use, reference should be had to the accompanying drawings and descriptive matter in which I have illustrated and described preferred embodiments of the invention.

Of the drawings:

Fig. 1 is a diagrammatic illustration of a scrubbing tower embodying one form of the present invention;

2,771,281 Patented Nov. 20, 1-956 "ice Figs. 2, 3 and 4 each illustrate a different pumping system modification of apparatus shown in Fig. 1;

Fig- 2a illustrates apparatus for operating two pumps from one motor;

Fig. 5 illustrates structural modifications which may be made in the recirculating pump shown in Fig. 4; and

Fig. 6 is an elevation of an impeller shown in section in Fig. 5.

The embodiment of the invention shown diagrammatically by way of example in Fig. 1, comprises a scrubbing tower 1 which is provided with a lateral gas inlet 2 adjacent its lower end, and a lateral gas outlet 3 adjacent its upper end. .The scrubbing chamber in the tower 1 is divided into upper, intermediate and lower stages or sections a, b and 0, respectively. The sections a and b are separated by a liquid collecting device a, and the sections b and c are separated by a liquid collecting device b which may be, and as shown is substantially similar to the device a. A portion of the Fig. l tower structure is shown in Fig. 2 on a larger scale and in greater detail and only partly in section. As is hereinafter explained, the apparatus shown in Fig. 2 differs from the Fig. l apparatus operatively and structurally only in respect to pumping and piping provisions.

The liquid collecting device b shown diagrammatically in Fig. 1, and in more detail in Fig. 2, comprises an annular liquid receiving chamber 4b. The latter is formed by securing an annular flange member 5 having an outturned lower edge portion to the inner side of the tower shell, by welding or riveting. The body of the member 5 is in the form of a section of a hollow cone coaxial with the tower. A louver structure above and associated with the member 5, comprises three superposed coaxial annular members 6, 7 and 8 above and at successively increasing distances from the member 5 and a top member 9 which may comprise a hollow cone body portion. Each of the members 6, 7 and 8 is in the form of a section of a hollow cone. The upper and lower edges of the member 7 respectively overlap the lower edge of the member 8 and the upper edge of the member 6. The lower edge of the member 6 overlaps the upper edge of the subjacent member 5, and the lower or outer edge of the top member 9 overlaps the inner upper edge of the member 8. The members 5, 6, 7, 8 and 9 are vertically displaced to provide an annular gas outlet, or louver opening beneath each of said members 6, 7, 8 and 9.

The collecting device a shown in Fig. 1, may be structurally identical to the collecting device b except in certain respects hereinafter mentioned, but for convenient identification, the annular liquid receiving space of the device a is designated 4a. The members 6, 7, 8 and 9 of each collecting device a may be supported in any convenient manner.

Scrubbing oil is sprayed into the upper end portion of the scrubbing space a by a plurality of spray nozzles 11. As shown, the spray nozzles 11 are all located at the same level, though this is not essential, and are arranged to discharge downwardly directed jets into the subjacent portion of the scrubbing chamber. The scrubbing oil is supplied to the nozzle 11 by branch pipes from a scrubbing oil supply pipe 12. In ordinary practice, oil will be passed into the pipe 12 by pumping means not shown, which may receive oil directly or indirectly from the outlet of the associated debenzolizing apparatus, not shown, to which the oil passing through the tower 1 is passed, for the separation from the scrubbing oil of those benzol constituents absorbed from the gas passing through the scrubbing tower. A suitable amount of fresh make-up scrubbing oil may be added to the scrubbing oil returned to the tower from the debenzolizing apparatus.

Scrubbing oil is sprayed into the upper portion of the wisp scrubbing space 11 by nozzles shown as comprising a. I

central upper nozzle 13, a plurality of intermediate nozzles 14 and a plurality of lower nozzles 15. As shown, the nozzle 13 is centrally disposed in the dome-shaped louver structure of the device a, beneath and in close proximity to the top member 9 of that structure. The intermediate nozzles 14 are shown as located at a level slightly below the bottom of the liquid receiving chamber 4. The spray nozzles 15 of the space I; are located at a level below that of the nozzles 14 and above that of the top member of the louver structure b. In Fig. 1, each of the nozzles 13, 14 and 15 spraying liquid into the scrubbing space b, receives liquid through an individual branch supply pipe 16 from a buss pipe 17 extending 15 circularly about the tower 1 at a'level which advantage-- ously, and as shown, is intermediate the levels of the nozzles 13 and 15 discharging into the scrubbing space b. A buss pipe 170, like the buss pipe 'or manifold 17, is shown as located below the trough 4b, and arranged to spray oil into the space through nozzles 13, 14' and. similar to the nozzles 13, 14 and 15 respectively.

As is hereinafter explained, oil sprayed into the space at through the nozzles 11 is successively collected in and withdrawn from collecting troughs 4a and 4b and the chamber 23 in the lower end portion of the tower, and is returned under pressure to the manifold 17 for respraying into the space I), and is returned under pressure to the manifold 17a for respraying into the space 0, as is hereinafter explained. Insofar as above described, the apparatus shown in Fig. l of the present application does not differ in principle from apparatus shown in my aforereferred to patent No. 2,675,215. However, there are differences between the apparatus shown in Fig. 1 of the present application and the apparatus shown in said patent, which do not result from differences in form or proportions of the apparatus, but from differences in the manner in which wash oil is passed from collecting elements, such as 4a, 4b and 23, to spraying elements such as the manifolds 17 and 17a.

A comparison of the operating characteristics of the apparatus shown in Fig. l of the instant application and shown in Fig. l of said patent, is facilitated by the fact that the two tower structures are similar in form and the fact that the reference symbols 1 to 17a are similarly applied in Fig. 1 of each application. In the comparison it will be assumed that the towers shown in Fig. l of the instant application and the prior application are, similarly proportioned. It will be further assumed, for example, that each tower is 100 feet high and 7 feet in diameter; that wash oil is sprayed into the space a of each tower through the corresponding nozzles 11 at the rate of 290 gallons per minute; that wash oil is resprayed into each of the spaces b and c at the rate of 230 gallons per minute; and that the collecting trough 4a is 2 feet above the trough 4b. None of the values just assumed are critical.

In the contemplated operation of the tower shown in Fig. 1 of the instant application, the major portion of the oil collecting in the trough 4a is passed to the inlet of a recirculating pump 19 through a pipe 20 which opens into the lower portion of the trough 4a. The pump 19 passes oil under pressure to th manifold 17 through a pipe 18 connecting the outlet of the pump 19 to the manifold 17. The portion of the wash oil collecting in the trough 4a and not withdrawn through the pipe 20, overflows into the trough 4b through a pipe 21 which has its upper end opening into the upper portion of the trough 4a. A relatively small portion of the Wash oil collecting in the trough 4b is withdrawn from that trough through a pipe 22 by a pump 19 which discharges into the pipe 18 through a pipe 18' receiving liquid through the outlet from the pump 19'. The bulk of the wash oil collecting in the trough 4b is withdrawn from the trough through a pipe 29a by a pump 1%. The latter discharges through a pipe 18a into the inanifold 17a. Oil not withdrawn from the trough 4b by-the pumps 19' and 19a, overflows through a pipe 21ainto a chamber 23 in the lower end portion of the space 0. Th chamber 23 is also adapted to receive liquor sprayed into the space 0 and accumulating in the lower end of that space. Wash oil is withdrawn from the chamber 23 by a pump 19a which discharges through a pipe 18'a into the pipe 1311 through which liquor is passed into the manifold 17a.

A pump 24 draws benzol enriched scrubbing oil away from the lower end portion-of the tower 1 shown in Fig. 1 of the present application, and passes the benzol enriched oil directly or indirectly to associated debenzolizing apparatus, not shown.

In the apparatus shown in Fig. 1 of said Patent No. 2,675,215, all of the wash oil entering the manifold or buss pipe 17 is passed to the latter by the pump 19 which draws all of the oil passed to the manifold 17 through apipe connecting the inlet of the pump 19 to the trough 4b. Furthermore, all of the wash oil collecting in the trough 4a is passed into the trough 4b through an overflow pipe 21 which discharges all. of the oil passing through it into the last mentioned trough. In normal operation, the amount of wash oil passed into the manifold 17 by the pumps 19 and 19, includes all of the oil sprayed into the space a and collected in the trough 4a, and includes a small portion of the oil sprayed into the space 11 through the nozzles 13, 14 and 15, and collected in the trough 412 from the space b, and received from the trough 4a through the overflow pipe 21. The amount of wash oil sprayed into each of th manifolds '17 and 17a, will exceed the amount of wash oil sprayed,

into the space'a through the nozzles 11 by an amount which may be varied by adjustment of the various regulating valves 25 shown in Fig. 2, but omitted fromFig. l and other figures to simplify the drawings. In practice, the amount of wash oil sprayed into each of the spaces b and 0 may well be 230 gallons per minute.

Computations involving certain reasonable assumptions which I have made, indicate that the theoretical horse-power required to spray wash oil into the space I: through the nozzles 13, 14 and 15 at the rate of 230 gallons per minute, requires an expenditure of 1.825

horse-power, whereas with the same assumptions the pumping energy required to spray 230 gallons of wash oil per minute through thesame nozzles 13, 14 and 15 with the pump and piping arrangement shown in Fig. l of my original application, requires an' expenditure of 3.12 horse-power.

In my'above mentioned computations, I have made use of the well known fact that the actual or brake horsepower of a pump moving a given volume of liquid of a given specific density against a total head or back pressure opposing the movement of the liquid, may be determined by the use of the following equation:

The symbols used in the foregoing equation have meanings or values as follows:

B. H. P.=hydraul ic horse-power G.' P. M.='gallons per'minute H=total head in feed of liquid szspecific gravity of the liquid :pump driving motor efficiency of the nozzle '13. The pipe frictionv loss is assumedto.

correspond to a total head loss of about feet; and the passage of the oil through the nozzles 13, 14 and 15 is assumed to result in a total nozzle pressure loss corresponding to a head of 10 feet. In each of the following equations including the factor 0.7, that factor is assumed to indicate a pump driving motor efliciency of 70%. The sum of the actual oil head and the friction and nozzle losses is thus assumed to equal a total dynamic head of 25 feet. With the foregoing assumptions, the horse-power used in operating the pump 19 will be given up by the following Equation 2:

195 25 0.8 B. H. P. 3960XQ7 -14 (2) In the operation of the pump 19' of Fig. 1 of the present application, the total dynamic oil head is assumed to be 25 feet, i. e., the difference between the liquid level in the trough 4b and the discharge level of the nozzle 13; and the friction loss is assumed to correspond to a head loss of 5 feet and a nozzle pressure loss is assumed to be 10 feet, as in Equation 2. The assumption that the head loss due to friction is not 10 feet but 5 feet in Equation 2, is based on the fact that the length of the flow path for the liquid passing through the pump 19 from the liquid level in the trough 4b to the nozzle 13, is approximately half the length of the flow path through the pump 19, which includes the pipes 20, 18 and 16 to the nozzle 13. With the foregoing assumptions, the horsepower used in operating the pump 19 will be given by the following Equation 2a:

eration of the pumps 19 and 19' of application Fig. 1 is thus:

B. H. P. 0.4 (2a) B. H. P.=1.4+O.4=1.8 (2b) As will be apparent, Equation 2b will apply directly to the horse-power required for the operation of the pumps 19a and 19'a of Fig. 1 unless the distance between the liquid levels in the trough 4b and chamber 23 differs significantly from the distance between the liquid levels in the troughs 4a and 4b.

On the assumption that the only difference between the means for spraying wash oil into the section b of the tower shown in Fig. l of the prior application, and the means illustrated and described for spraying liquor into the section b of the tower shown in Fig. 1 of the instant application, is due to the non-use in the prior application of the pump 19', the horse-power required for the operation of the pump 19 is obviously given by the following equation:

In the foregoing Equation 3, the factor 230 is indicative of the fact that all of the oil sprayed into the space b is pumped into the manifold 17 from the trough 4b by the pump 19. In said equation, the factor 45 represents the total dynamic head against which the pump 19 operates. As will be apparent, the value 3.0 is computed in the same manner as were the final horse-power values obtained in Equations 2 and 2a. In consequence, the relative effects of error in any of the numerator factors of the Equations 2, 2a and 3 could have only a relatively small effect on the relative final values of Equations 3 and 2b.

Fig. 2 includes a reproduction on a larger scale of the portion of the tower 1 of Fig. l which includes the space b and small adjacent portions of the spaces a and c. In Fig. 2, each of the .various pipes through which wash oil is passed into the tower, includes a valve by which the flow through the pipes can be interrupted or throttled. The use of such valves is ordinarily advantageous. The valves are omitted in Fig. 1 to simplify the drawing.

The only operative difference between the apparatus shown in Fig. 1 and that shown in Fig. 2, is that in Fig. 2, the pipe 18' through which oil is discharged by the pump 19' is connected to the pipe 20 which passes oil into the pump 19, instead of being connected to the pump outlet pipe 18 as it is in Fig. 1. This difference in pump connections materially reduces the pumping energy required, as is shown by the following Equation 4 which includes the factors, analogous to those included in the Equations 2 and 2a, used in deriving the Equation 2b:

In Fig. 3 I have illustrated a modification which differs from Figs. 1 and 2 in that the pump 19 is connected to the trough 4a and to the manifold 17 by pipes 20 and 18, respectively, but is not connected to the trough 4b or to the nozzles 15. However, in Fig. 3 an auxiliary pump 19' draws oil from the trough 4b through a pipe 22 and discharges oil through a pipe 18b to the manifold 17b which surrounds the tank structure 1 and supplies oil to the nozzles 15 discharging into the space b, as do the nozzles 14 which receive oil through the manifold 17 and pipe 18 from the pump 19. As will be apparent, the pumping energy required for the operation of the pump 19 of Fig. 3 is shown by the following Equation 5:

Fig. 4 illustrates a modification which differs from the form of the invention illustrated in Fig. 2 only by the omission of the pump 19, and by the direct connection of the trough 4b to the inlet of the pump 19 by a pipe 22a. In consequence, the pump 19 receives oil from the trough 4a through the pipe 20 and also receives oil through the pipe 22a from the trough 4b. Theoretically the omission of the pump 19 and the direct connection of the trough 4b to the pump 19 by the pipe 22a, merely increases the horse-power required for the operation of the pump 19 by an amount corresponding to the horse-power required for the operation of the pump 19' of Fig. 2. In consequence, the foregoing Equation 4 applies as well to the structure shown in Fig. 4 as to the structure shown in Fig. 2.

Fig. 5 illustrates by way of example, the internal structure of a pump 19c especially adapted for use in mixing, and for discharging the mixture of two fluids separately supplied to the pump through pipes 20 and 22a connected to the troughs 4a and 4b, as are the pipes 20 and 22a of Fig. 4.

The centrifugal pump 30 shown in Fig. 5 comprises an impeller 31 carried by a rotatable shaft 32 and arranged to rotate in an impeller chamber 33 coaxial with and surrounding the shaft 32 and enclosed by the stationary pump casing 34. The impeller 31 may be of any usual or suitable type except as to the form of its vanes. One form of pump which may be used is shown in Fig. 6. The casing 34 is formed with an inlet 35 coaxial with the shaft 32 and opening into the impeller chamber 33, and increasing in cross section as the distance from the impeller chamber .33 decreases. The passage 35 is surrounded by an annular chamber 37 which is also tapered and has its large diameter end opening into the impeller chamber 33. As illustrated, the discharge end of a pipe 22a has an outturned flange abutting against and bolted or otherwise suitably anchored to the flanged outer end of the casing structure surrounding the passage 35. As shown, the casing is formed with an inlet 38 transverse to the axis opening into the inlet passage 37, and provided with a flanged outer end against which the flanged inlet end of a pipe 21) is secured. The impeller chamber opens at its periphery into a conventional outlet channel 39 which surrounds and is in communication with the impeller chamber. The final values shown in Equation 2b, 3, 4 and 5 are approximate only, but dilfer from the theoretically exact brake horse-power values by not more than about 0.05.

In the contemplated use or" the form of the invention shown in Fig. 5, the liquid passing into the pump through the pipe 2'!) is under a head of twenty feet or so greater than the head of the liquid passing into said pump through the pipe 22a. To suitably increase the pressure at which the liquid supplied through the pump inlet passage passes into admixture in the impeller chamber 33 with the liquid supplied to said chamber from the pump passage 37, the impeller is provided with vane portions 31b acting directly on the liquid passing into the impeller chamber 33 from the passage 35. As shown in Fig. 5, the vane portions 311; may be inner end extensions of the vanes 31a. To further increase the pressure of the liquid supplied through the inlet passage 35, the lower end of the conical wall surrounding the inlet passage 35 may be shortened and the width of the vane portion 3112 may be correspondingly increased.

The various conventionally illustrated pumps 19, 19, 19a and 22a shown in Figs. 1 to 4, are ordinarily motor driven, and may be each driven by a separate motor. However, in some cases at least, it may well be practically advantageous to drive each pair of pumps associated with one another, as are the pumps 19 and 19, 1% and w'a, by a single motor. Thus as shown in Fig. 2a, a motor 40 may have one end 41 of its rotor shaft directly connected to the impeller of the pump 19 and have the other end, 41', of said shaft connected to tie impeller of a smaller pump 19' through a pair of spur gears 42 and 43. As shown, the gear 42 is mounted on the motor shaft end 41 and the spur gear 43 is connected to the impeller shaft 44 of the smaller pump 19'. As illustrated, the gears 42 and 4-3 are of the same diameter so that the shafts 41 and 44 have the same rotative speed. However, the gears 42 and 43 may differ in diameter so that the pumps 19 and E9 of Fig. 2a will have different rotative speeds.

Regardless of the relative diameters of the gears 42 and 43, the arrangement shown in Fig. 2a is effective to rotate the impeller of each of the pumps 19 and 19 in the right direction when the two pumps are of such design that each is operative only when its impellers rotate in one particular direction, as is customary. Thus, for example, when each impeller is analogous in type to the impeller shown in Fig. 6, each impeller must rotate in the clockwise direction when viewed from the side'of the impeller shown in Fig. 6. Such rotation is made possible in Fig. 2a, wherein one of the pumps 19 and 19' is displaced l80 about a vertical axis relative to the other pump, by the gears 42 and 4 3 which connect the impeller shafts 41 and 44-. When connected as shown in Fig. 2a, the shafts 41 and i l must rotate in opposite directions if both impellers are of the character shown in Fig. 6, and are similar in design.

I have referred herein, by way of illustration and example, to the use of the invention in a scrubbing tower having a height of 100 feet and a diameter of 7 feet, and to the introduction of scrubbing oil into the top of the tower at the rate of 200 gallons per minute. However, the invention may advantageously be used in scrubbing towers which are taller and much larger in diameter than the tower referred to by way of example. As will be apparent also, the form of the tower and associated apparatus with which the invention is used, may take different forms. In some cases it may be desirable to return liquid withdrawn from one or both of collector elements 4.4 and 4b at the opposite ends of a tower section, partly to that section and partly into an adjacent section. Thus as shown in Fig. 3, liquid withdrawn from the trough 4a is sprayed into the section I; through nozzles 13 and 14, and is sprayed into the tower section a through a manifold 16a and nozzles 1615.

While in accordance with the provisions of the statutes,

I have illustrated and described the best forms ofembodi ment of my invention now known to me, it will be apparent to those skilled in the art that changesmay be made in the forms of the apparatus disclosed without departing from the spirit of my invention as set forth in the appended claims, and that in some cases certain features of my invention may be used to advantage without a cor into an upper section of said tower and for withdrawing downwardly moving scrubbing liquid from separate collector chambers adjacent the lower ends of two adjacent tower sections, and means for pumping from each of said chambers liquid separately collected in said two separate collector chambers and returning the liquid so pumped in spray form partly into said lower section and partly into another tower section in end-to-end relation with said lower section. j

2. Apparatus for separating vapor from a gaseous liuid, comprising a vertical housing having an inlet for said fluid adjacent the bottom thereof and an outlet for said fluid adjacent the top thereof, means for dividing said tower into a plurality of stacked sections, said last mentioned means being adapted to permit the substantially unrestricted passage of said gaseous fluid upwardly from section to section and to prevent the passage of liquid downwardly from section to section whereby to collect liquid introduced into a section at the bottom thereof, means for introducing scrubbing liquid into two adjacent sections, the liquid introducing means in the lower of said two sections being located adjacent the top thereof, and means for pumping from each of the bottoms of said two separate sections liquid separately col lected adjacent each of the bottoms of said two separate sections to said liquid introducing means in said lower section whereby to supply said lower section with liquid separately pumped from said two separate sections.

3. Apparatus for separating vapor from a gaseous iluid, comprising a vertical housing having an inlet for said fluid adjacent the bottom thereof and an outlet for said fluid adjacent the top thereof, means for dividing said tower into a plurality of stacked sections, said last mentioned means being adapted to permit the substantially unrestricted passage of said gaseous fluid upwardly from section to section and to prevent the passage of liquid downwardly from section to section whereby to collect liquid introduced into a section at the bottom thereof, means for introducing scrubbing liquid into two adjacent sections, the liquid introducing means in the lower of said two sections being located adjacent the top thereof, means for pumping from the bottom of the upper of said two sections liquid separately collected thereat to the liquid introducing means in said lower section, and other means for pumping from the bottom of said lower section liquid separately collected thereat to the liquid introducing means in said lower section, whereby liquid which is separately pumped from said two separate areas of collection is pumped to said liquid introducing means in said lower section v 4. Apparatus for separating vapor from a gaseous fluid, comprising a vertical housing having an inlet for said fluid adjacent the bottom thereof and an outlet for said fluid adjacent the top thereof, means for dividing said tower into a plurality of stacked sections, said last mentioned means being adapted to permit the substantially unrestricted passage of said gaseous fluid upwardly from section to section and to prevent the passage of liquid downwardly from section to section whereby to collect liquid introduced into a section at the bottom thereof, means for introducing scrubbing liquid into two adjacent sections, the liquid introducing means in the lower of said two sections being located adjacent the top thereof, means for pumping from the bottom of the upper of said two sections liquid separately collected thereat to the liquid introducing means in said lower section, and other means for pumping from the bottom of said lower section liquid separately collected thereat to the liquid introducing means in said lower section, whereby liquid which is separately pumped from said two separate areas of collection is pumped to said liquid introducing means in said lower section, said first mentioned pumping means being adapted to pump a greater amount of liquid than said other pumping means.

5. The method of scrubbing a gaseous fluid which consists in passing fluid upward through a vertically elongated scrubbing space, spraying a scrubbing liquid into an upper portion of said space, successively separately collecting said scrubbing liquid passing downward through successively lower sections of said space, pumping from each of two separate areas of collection liquid separately collected in each of said two areas of collection to spraying means in the lower of said two sections and respraying said liquid therein.

6. Apparatus for separating vapor from a stream of coke oven gas, comprising a scrubbing tower enclosing superposed scrubbing sections, means for passing a stream of gas upward through said sections, means for spraying a vapor absorbing liquid into an upper one of said sections, an isolated collector means adjacent the bottom of each of two adjacent tower sections for separately collecting downwardly moving scrubbing liquid thereat, means for spraying liquid into the lower of said two sections, and pumping means having separate intake means extending to each of said collecting means and outlet means extending therefrom to said spraying means, whereby separately collected liquid is pumped by said pumping means from both said collector means to said spraying means for respraying in said lower section.

7. Apparatus as specified in claim 6, wherein said pumping means includes a single pump having two intakes, one each of said intakes extending to one each of said collecting means, said pump further having an outlet extending therefrom to said spraying means, whereby said single pump pumps from each of said two separate collector means liquid separately collected in each of said two separate collector means to said one spraying means.

8. Apparatus as specified in claim 6, wherein said pumping means comprises two pumps, one of said pump? having an intake extending to the lower of said collector means and the other of said pumps having an intake extending to the upper of said collector means, and both said pumps having outlets extending to said spraying means, whereby said two pumps pump from each of said two separate collector means liquid separately collected in each of said two separate collector means to said one spraying means.

9. Apparatus as specified in claim 8, wherein said one pump is effective to pass liquid pumped from said lower collecting means into admixture with the liquid pumped from said upper collecting means by said other pump.

10. Apparatus as specified in claim 8, wherein the two pumps withdrawing liquid from the collector means adjacent the lower ends of both sections have rotary impellers and a common motor is connected to and rotates each pump impeller in the direction required for the pas- I sage of the liquids discharged by the two pumps into a common output conduit.

11. Apparatus as specified in claim 6, including one pump having a rotor and withdrawing liquor from the upper collector means, a second pump having a rotor and withdrawing liquid from said lower collector means, a pump rotating motor having a rotating shaft with one end directly connected to the rotor of one of said pumps and a reversing gear connecting the rotor of the second pump to the other end of said shaft.

12. Apparatus for separating vapor from a stream of coke oven gas, comprising a coke oven tower enclosing superposed scrubbing sections, means for passing a stream of coke oven gas upwardly through said tower, means for spraying vapor absorbing liquid into an upper portion of each of two adjacent scrubbing sections, means for collecting said liquid adjacent the bottoms of said two adjacent sections, a rotary impeller pump having an impeller chamber and an impeller with vanes mounted in said chamber for rotation about an axis, said pump further having a first intake means extending from one of said collector means to said impeller chamber at one distance from said axis, a second intake means extending from the other of said collector means to said chamber at another distance from said axis, and outlet means extending from the periphery of said chamber to the lower of said two spraying means, whereby said pump pumps from each of said two separate collector means liquid separately collected in each of said two separate collector means to the lower of said two spraying means.

References Cited in the file of this patent UNITED STATES PATENTS 1,952,099 Shoeld Mar. 27, 1934 2,080,713 Hayes May 18, 1937 2,554,428 Swearingin May 22, 1951 2,675,215 Otto Apr. 13, 1954 2,678,199 Koch May 11, 1954 FOREIGN PATENTS 551,359 Germany May 30, 1932 

